The present invention refers to an encapsulated apparatus, and in particular to a cast, explosion-proof electromagnet of a type including a coil and a ferromagnetic circuit which are arranged in a casing of plastic material or metal.
Encapsulation of explosion-proof electromagnets should ensure an electric insulation and prevent explosive gas mixtures from reaching ignition sources. Moreover, such cast electromagnets should withstand mechanical stresses and should be protected from chemical influences, and the encapsulation should be tear-resistant, heat and cold-resistant, chemical-resistant and should display good bonding behavior.
Conventional electromagnets are embedded in a casting compound of cast resin. Practice has shown, however, that flexibility-providing compounds escape from the cast resin resulting in embrittlement and shrinkage and thus to tearing or cracking. Eventually, the casting compound may detach from the casing or the casing may become deformed. Therefore, the casting compound cannot ensure the electric insulation of the electromagnet and provide protection from explosion.